Adjustable blade turbines

ABSTRACT

A turbine, adaptable to improve the survivability of fish present in water flowing therethrough, includes a hub and associated runner blades. Each blade comprises an inner edge and a distal outer edge, a leading edge and a trailing edge separated by a water directing surface. Each blade is rotatable relative to the hub about a blade rotational axis. The turbine is provided with features designed to shield a gap formed between the hub and the blade inner edge as the blade is rotated about its axis.

FIELD OF THE INVENTION

The present invention relates generally to hydroelectric turbineinstallations. More particularly, this invention pertains tohydroelectric installations utilizing propeller-type turbines in whichthe angular position of the runner blades relative to the hub of theturbine or propeller, i.e. the pitch of the blades, is adjustable.

BACKGROUND OF THE INVENTION

Hydroelectric turbine installations in which the turbine comprisesseveral runner blades having an adjustable pitch are widely used. Inthese turbines, each runner blade (often simply called a "blade"), ispivotally connected to the hub and rotatable about an axis extending ina direction generally perpendicular to the hub. The rotation of eachblade about its axis permits the turbine operator to seek optimumefficiency of the hydroelectric installation under the entire range ofoperating conditions of the turbine. In the hydroelectric industry,turbines with adjustable pitch blades are commonly referred to as"Kaplan turbines". Kaplan turbines are also typically provided withadjustable wicket gates designed to regulate the flow of water admittedto the turbine.

It is well recognized that hydroelectric power generation is generallysocially more desirable than its counterparts which obtain energy fromthe combustion of fossil fuel or the fission or fusion of atoms. It isalso widely accepted that Kaplan turbines materially improve theefficiency of hydroelectric installations. However, it is increasinglybeing suspected that certain Kaplan installations have variousdetrimental impacts on the environment, particularly on the fishpopulation which is present in the water flowing through the turbine.

One of these potentially adverse impacts results from the very featuresof Kaplan turbines that increase the efficiency of hydroelectricinstallations using these turbines. Specifically, in a Kaplan turbinehaving its main axis generally vertical, the pitch of the blades isadjustable from maximum blade opening or pitch, i.e., when the face ofeach blade is almost parallel to the main turbine axis, to minimum bladeopening or pitch in which case the face of each blade is placed in aflatter position (i.e., generally perpendicular to the flow of water fedto the turbine). In Kaplan turbines having a non-fully sphericalupstream hub, when the blade is at low pitch a gap is created betweenthe hub and the leading edge of the blade (i.e., upstream of the axis ofrotation of the blade relative to the hub), as illustrated for examplein FIG. 26.

Various studies have shown that these gaps have several detrimentaleffects. First, a gap between the hub and the blade creates cavitationdue to water leakage occurring through the gap. Significantly, the gap(particularly upstream of the blade rotational axis) is also a trap forfish which are present in the water flowing through the turbine. It isbelieved that fish flowing into the gap have a significantly greaterchance of being injured or killed than fish flowing through otherregions of the turbine.

Recent efforts have therefore been undertaken to address the apparentpropensity of Kaplan turbines to injure fish. For example, systems havebeen designed to divert fish away from Kaplan turbines. These systemsinclude screens to keep fish out of the turbine, or structures designedto divert fish away from the turbine. It can be readily appreciated,however, that these prior art structures have several shortcomings.First, systems of the type necessitating separate structures consumesome of the water normally flowing through the turbine thereby reducingthe energy produced by the turbine installation. Second, it has beenfound that these systems are not fully effective to divert the entirefish population away from the turbine. In addition, screens disturb thewater flow and cause efficiency losses within the turbine. Finally, ascan be readily appreciated, these additional structures, which inaddition to not being entirely satisfactory, materially increase thecost of hydroelectric installations using Kaplan turbines.

Various attempts have also been made to increase the efficiency ofadjustable pitch propellers and turbines by reducing the gap formed inthese mechanisms. For example, U.S. Pat. No. 2,498,072 issued Feb. 21,1950 to Dean discloses an aircraft propeller in which the pitch of theblades is adjustable. To reduce air turbulence and drag in the region ofthe gap formed at the base of the blade, a seal made of molded rubber isattached to the hub embracing the blade airfoil. Still another exampleof an approach used to improve the operating characteristics or airpropellers is illustrated in U.S. Pat. No. 2,378,958 issued on Jun. 26,1945 to Troller. In Troller, to minimize noise and air turbulence, therim of the propeller having a cylindrical outer surface is provided witha recess to receive the base portion of the blade. The close tolerancebetween the base of the blade and the recess generally improves theoperation of the propeller. The inventors of the present invention arealso aware of the use in the late 1920's of a technique somewhat similarto that disclosed in Troller to attempt to increase the efficiency ofKaplan turbines.

The foregoing indicates that various attempts have been made to increasethe efficiency of air propellers and Kaplan turbines. However, none ofthese attempts have been utilized to increase the survivability of fishas they pass through these turbines. Moreover, in view of the fact thatprior art systems and methods to divert fish away from Kaplan turbineare costly and not fully satisfactory, there is a need to find otherways to lessen the ability of Kaplan turbines to injure fish, therebyenhancing the environmental characteristics of these turbines, whileincreasing, or at least not impairing the overall efficiency of theseinstallations.

SUMMARY OF THE INVENTION

The present invention improves the survivability of fish present inwater flowing through a turbine of the type comprising a hub and aplurality of blades pivotally connected to the hub.

A turbine in accordance with one aspect of the present inventioncomprises a hub and associated blades. The angular position of eachblade relative to the hub (i.e., the pitch of each blade) is adjustable.The turbine is provided with means to shield the gap formed between theinner edge of each of the blades and the hub as the blades are adjustedfrom maximum to minimum pitch, thereby preventing fish from being caughtin the gap.

According to a further aspect of the present invention, thesurvivability of fish is increased by providing the turbine installationwith features that effectively divert fish away from the gap.

According to another aspect of the invention, the turbine installationincludes means to increase the survivability of fish by reducing orshielding gaps formed in other areas of the installation.

According to yet another aspect of the invention, the turbineinstallation is provided with features that, in addition to improvingthe survivability of fish, also increase the efficiency of theinstallation.

Other advantages of the invention will become apparent from the detaileddescription given hereinafter. It should be understood, however, thatthe detailed description and specific embodiments are given by way ofillustration only since, from this detailed description, various changesand modifications within the spirit and scope of the invention willbecome apparent to those skilled in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

The preferred exemplary embodiment of the invention will hereinafter bedescribed in conjunction with the appended drawings, wherein likenumerals denote like elements and:

FIG. 1 is an elevational view, partially in cross section, of ahydroelectric installation including a turbine with adjustable blades;

FIG. 2 is a perspective view of a first embodiment of the hub and oneassociated blade, the blade being shown at maximum pitch position;

FIG. 3 is a perspective view of the hub and blade of FIG. 2, the bladebeing shown at minimum pitch position;

FIG. 4 is a perspective view of a hub and one associated blade accordingto another aspect of the present invention, the blade being shown atmaximum pitch position;

FIG. 5 is a perspective view of the hub and blade of FIG. 4, the bladebeing shown at minimum pitch position;

FIG. 6 is a top plan view of the hub shown in FIG. 4, with the region ofa blade pocket shown in partial section view;

FIG. 7 is a cross-sectional view of the hub and blade shown in FIG. 4;

FIG. 8 is a top plan view of the hub and one associated blade inaccordance with another embodiment of the present invention, showing aplurality of spring-biased fingers;

FIG. 9 is an enlarged perspective view of a portion of the inner edge ofthe blade shown in FIG. 8;

FIG. 10 is an enlarged partial sectional view of the blade and hub shownin FIG. 8;

FIG. 11 is a top plan view of the hub and one associated blade inaccordance with another embodiment of the present invention, showing aplurality of blade water jets;

FIG. 12 is an enlarged perspective view of a portion of the inner edgeof the blade shown in FIG. 11;

FIG. 13 is an enlarged partial sectional view of the blade and hub shownin FIG. 11;

FIG. 14 is a top plan view of the hub and one associated blade inaccordance with another embodiment of the present invention, showing aplurality of hub water jets;

FIG. 15 is a front elevational view of the hub and blade shown in FIG.14;

FIG. 16 is an enlarged partial sectional view of the blade and hub shownin FIG. 14;

FIG. 17 is a top plan view of the hub and one associated blade inaccordance with another embodiment of the present invention, showing aboot fitted onto a portion of the inner edge of the blade;

FIG. 18 is a front elevational view of the hub, blade and boot shown inFIG. 17;

FIG. 19 is an enlarged partial sectional view of a first configurationof the boot used with the blade and hub shown in FIG. 17;

FIG. 20 is an enlarged partial sectional view of a second configurationof the boot used with the blade and hub shown in FIG. 17;

FIG. 21 is a perspective view of the hub and one associated blade inaccordance with another embodiment of the present invention, showingraised areas formed on the hub outer surface;

FIG. 22 is a front elevational view of the hub shown in FIG. 21;

FIG. 23 is a perspective view of the hub and one associated blade asshown in FIG. 21, showing the hub also comprising a pocket formedtherein;

FIG. 24 is a front elevational view of the hub shown in FIG. 23;

FIG. 25 is a front elevational view of another embodiment of the presentinvention showing an inflatable shroud in deflated condition;

FIG. 26 is a front elevational view of the embodiment of FIG. 25 showingthe inflatable shroud in inflated condition;

FIG. 27 is a partial front elevational view of the hub and blades inaccordance with the present invention showing a spherical dischargering;

FIG. 28 is a front elevational view of the hub and blades in accordancewith the present invention showing a downstream spherical hub androunded blade outer edge;

FIG. 29 is a top plan view of a typical rotatable blade embodyinganother aspect of the present invention;

FIG. 30 is a partial cross-sectional view of a portion of the inner edgeof the blade of FIG. 29 taken along line 30--30 shown in FIG. 29;

FIG. 31 is a partial cross-sectional view of a portion of the inner edgeof the blade of FIG. 29 taken along lines 31--31 shown in FIG. 29;

FIG. 32 is a front elevational view of the blade shown in FIG. 29;

FIG. 33 is a partial cross-sectional view of a portion of the leadingedge of the blade of FIG. 32 taken along lines 33--33 shown in FIG. 32;

FIG. 34 is a partial cross-sectional view of a portion of the leadingedge of the blade of FIG. 32 taken along lines 34--34 shown in FIG. 32;and

FIG. 35 shows a block diagram of the closed-loop control systemsassociated with a turbine of the present invention.

DETAILED DESCRIPTION OF A PREFERRED EXEMPLARY EMBODIMENT

The present invention relates generally to hydroelectric installationshaving turbines provided with features designed to improve thesurvivability of fish present in water flowing through the turbines. Theturbines are of the type comprising a hub and a plurality of bladespivotally connected to the hub. It should be understood, however, thatthe invention is applicable to any other type of turbine or propeller inwhich the blades are pivotally adjustable with respect to the hub.

Referring to FIG. 1, a hydroelectric installation generally designatedas 10 comprises a passageway 12, in which water flows from an upperelevation source in fluid communication with the upstream end 14 ofinstallation 10, to a lower elevation discharge region 16. Installation10 also includes a turbine 18 of the type comprising a hub 20 having alongitudinal axis 22, and a plurality of runner blades 24 pivotallyconnected to hub 20. Each blade 24 is movable about a rotational axis 26extending in a direction generally perpendicular to longitudinal axis22. While the present invention will be described with reference toturbine 18 in which longitudinal axis 22 is vertical as shown in FIG. 1,those skilled in the art will appreciate that the present invention issimilarly applicable to turbines disposed horizontally or at anyposition deviating from the horizontal or vertical, depending on theparticular configuration of passageway 12. Additionally, axes ofrotation 26 could be inclined relative to longitudinal axis 22 withoutin any way departing from the scope of the present invention.

Intermediate upstream end 14 and rotational axis 26 is disposed adischarge ring 27 which directs the flow of water from upstream end 14toward turbine 18. Installation 10 includes several wicket gates 28,which may be adjusted in rotation to regulate the flow of water admittedto passageway 12, and stay vanes 30 which are designed to support theportion of installation 10 located above turbine 18, that is, the thrustbearing 32, generator 34, and associated control systems and componentstypically located in the power station, some of these systemsconstituting what is commonly known in the industry as the "governor".

Referring now more particularly to FIGS. 2 and 3, hub 20 comprises anupstream region 36 and a downstream region 38 located on the upstreamand downstream sides of rotational axis 26, respectively. Turbine 18also typically includes between 2 and 9 runner blades 24. However, inthe various Figures only one blade will be represented to facilitate thedescription of the present invention.

Each blade 24 comprises a hydrofoil generally designated as 40 having aninner edge 42 and a distal outer edge 44, a leading edge 46 and atrailing edge 48 separated from leading edge 46 by a water directingsurface 50. Blade 24 is disposed for rotational movement relative to hub20 with its inner edge 42 proximate to the outer surface 52 of hub 20.Hub 20 is generally hollow, the hollow cavity 54 being defined by aninner surface 56 which is spaced apart and oppositely faces outersurface 52. Cavity 54 conveniently houses the various mechanisms,linkages and other systems necessary for the rotation of blades 24 aboutaxes 26. As illustrated in FIG. 2, when blade 24 is at maximum pitchposition, water directing surface 50 points in a direction generallyparallel to longitudinal axis 22. At minimum pitch position (asillustrated in FIG. 3), water directing surface 50 is substantiallyperpendicular to longitudinal axis 22.

In a first embodiment of the present invention, hub 20 includes afabricated shroud 58 disposed about outer surface 52, in the upstreamregion 36 of hub 20. Shroud 58 includes a plurality of cavities 60.Because shroud 58 is configured to substantially conform to outersurface 52, cavities 60 form with outer surface 52 pocket regions 62which are used to receive the portion 64 of leading edge 46 proximateinner edge 42 as blade 24 approach maximum pitch (as illustrated in FIG.2). Conversely, when blade 24 is at minimum pitch as shown in FIG. 3,portion 64 substantially comes out of pocket 62 without, however,forming a gap with spherically configured outer surface 52. This meansthat at minimum pitch, as well as at maximum pitch, there are no openregions formed between inner edge 42 and outer surface 52 of hub 20which are accessible to fish present in water supplied to turbine 18. Asa result, fish are not injured by blades 24 as they travel in passageway12 through turbine 18.

Alternatively, shroud 58 may also be formed integrally with hub 20, asillustrated in FIGS. 4-7. As shown in FIG. 7, at maximum pitch portion64 of blade 24 is received in pocket 62, thereby effectively eliminatingany gap between outer surface 52 and inner edge 42.

For various reasons, it may not be practical to use shroud 58 in certainhydroelectric installations. In those cases, other embodiments of thepresent invention may be used to reduce or shield the gap formed betweenthe inner edge of the blade and the hub of the turbine. Examples of suchother embodiments will now be discussed referring more particularly toFIGS. 8-16.

As illustrated in FIGS. 8-10, the gap generally designated as 66 formedbetween inner edge 42 and hub outer surface 52 can be substantiallyreduced or shielded by means of preferably a plurality of pins orfingers 68 matingly received in bores 70 formed in portion 64 of blade24. Each pin 68 is biased out of bore 70 toward outer surface 52 bymeans of a spring 72 acting on the end 74 of pin 68 opposite end 76which is in contact with surface 52. As a result, when blade 24 isrotated about its rotational axis 26, ends 76 of pins 68 remain incontact with outer surface 52, thereby effectively closing gap 66 sothat fish cannot be caught therein. Those skilled in the art willreadily appreciate that fingers or pins 68 can have variousconfigurations (not necessarily round in cross section), ends 76 canalso take different shapes (not necessarily rounded), or a single fingercan be used instead of a plurality of fingers, in each case withoutdeparting from the scope of this embodiment.

Turning now to the embodiment disclosed in FIGS. 11-16, there isprovided a plurality of water jets 78 dispersing water in gap region 66.Jets 78 comprise water passageways 80 formed in each of blades 24 fromleading edge 46 to inner edge 42. Although when blade 24 is positionedtoward maximum pitch, a resulting gap 66 is formed between outer surface52 and inner edge 42, the jets of water 78 which are injected in gap 66by water passing through passageways 80 effectively prevent fish presentin the water from entering gap 66. Alternatively, the water can beinjected into gap 66 from hub 20 as illustrated in FIGS. 14-16. In thatcase, water jets 78 comprise water passageways 80 formed in hub 20 andexiting therefrom at outer surface 52.

A further embodiment of the present invention will now be discussedreferring more particularly to FIGS. 17-20. In that case, gap 66 isshielded by a boot generally designated as 82. Boot 82 is preferablymade of a deformable material such as rubber connected to leading edge46 of blade 24. Boot 82 conveniently includes a skirt 84 ridingeffectively in contact with outer surface 52 of hub 20 during rotationof blade 24 about rotational axis 26. Skirt 84 may also be configured asa plurality of flexible members which remain substantially in contactwith outer surface 52. If sufficiently thin, these members may take theform of bristles brushing against outer surface 52 when blade 24 isrotated about axis 26. Conversely, the bristles or flexible members maybe attached to hub 20 in regions of outer surface 52 proximate portion64 when blade 24 is at minimum pitch. Alternatively, as illustrated inFIG. 20, boot 82 may comprise a membrane 86 filled with a pliable fluid88 thereby allowing boot 82 to remain effectively in contact with outersurface 52 during rotation of blade 24.

As we have seen earlier, pockets 62 represent an effective way to shieldgap 66 formed between inner edge 42 and outer surface 52 of hub 20. Incertain cases, however, cavity 54 needs to be as large as possible toaccommodate the various blade rotation mechanisms. This means that thedistance separating outer surface 52 from inner surface 56 (i.e., thethickness of the hub wall) may not be sufficient to permit the formationof pockets deep enough to effectively receive portion 64 and shield gap66. In certain cases, the wall thickness may even be such as to notpermit the formation of any pockets at all. Another embodiment of thepresent invention addresses situations where the thickness of the hubwall becomes a dominant consideration.

Referring more particularly to FIGS. 21-24, hub 20 includes severalraised areas 90 locally formed on outer surface 52 in regions of hub 20upstream of rotational axis 26. Areas 90 are therefore formed proximateleading edge 46 of blade 24 when blade 24 is at minimum pitch, as shownin FIG. 21. As a result, areas 90 shield gap 66 formed between inneredge 42 and outer surface 52. As shown in FIGS. 21 and 22, areas 90 canalso be formed downstream of rotational axis 26 in the event the bladeand hub construction is such that a gap 66 is also formed in that regionof turbine 18. Additionally, in cases where the hub wall thickness issufficient to form shallow pockets, as shown in FIGS. 23 and 24, severalareas 90 may also be combined with a plurality of pockets 62 formed atspaced intervals in outer surface 52. The number of pockets 62 does notnecessarily have to correspond to the number of raised areas 90 asvarious considerations including performance and cost may dictateotherwise. Furthermore, such considerations in light of particular huband blade configurations may also lead one to select a combination ofpockets 62 and areas 90 upstream or downstream only or both downstreamand upstream of rotational axis 26. The inventors of the presentinvention have noted, however, that, to improve the survivability offish passing through turbine 18 while limiting water turbulence createdby these "fish-friendly" features, it is generally preferable to usepockets 62 upstream of rotational axis 26 and raised areas 90 downstreamof rotational axis 26.

In certain other cases, it may be more convenient to increase thesurvivability of fish passing through hydro-turbines by associatingvarious features and mechanisms with other turbine elements, or bymodifying turbine components other than the hub of the turbine, asillustrated in FIGS. 25-32. Referring to FIGS. 25 and 26, gap 66 is, ineffect, shielded by an inflatable shroud 92 connected to a head cover 94typically disposed upstream of hub 20, i.e. upstream of blade rotationalaxis 26. Shroud 92 may comprise a single hollow piece of deformablematerial to form an inflatable region of predetermined length, or may beconfigured as a continuous inflatable belt surrounding the entireperimeter of head cover 94. In other cases, a plurality of shrouds 92may be disposed and attached at discrete locations around the perimeterof cover 94. Shroud 92 may also be attached to other components ofturbine 18 that are disposed about axis 22 upstream of gap 66. In allcases, however, the rubber-like material of shroud 92 cushions theimpact of fish against shroud 92 as they are deflected away from gap 66.

Shroud(s) 92 is (are) inflated as blades 24 are rotated from maximum tominimum pitch. The degree of inflation of shroud 92 may, advantageously,also be controlled to be in direct correlation with the position ofblades 24, i.e., going from minimum inflation at maximum pitch (as shownin FIG. 25), to maximum inflation at minimum pitch (as shown in FIG.26).

Referring to FIG. 27, turbine 18 is shown positioned in water passageway12 extending from upstream end 14 of installation 10 to a lowerelevation discharge region 16. Passageway 12 includes discharge ring 27disposed upstream of blades 24. Discharge ring 27 has a sphericalconfiguration to cooperate with outer edge 44 of blades 24 as blades 24are rotated about rotational axes 26. The spherical configuration ofdischarge ring 27 shields outer edge 44 of each of blades 24 from thepath of fish flowing through turbine 18, thereby increasing theirsurvivability. Still with reference to FIG. 27, passageway 12 furtherincludes a plurality of wicket gates 28. Wicket gates 28 are typicallyrotatable to control water flowing from upstream end 14. Each wicketgate 28 includes an upper edge 96 and a distal lower edge 98. Asillustrated in FIG. 27, the spherical configuration of discharge ring 27also advantageously cooperates with lower edge 98 to reduce a dischargegap 100 formed between discharge ring 27 and lower edge 98. As a result,spherical discharge ring 27 reduces the size of gaps commonly formedbetween ring 27, blade outer edge 44 and wicket gate lower edge 98,thereby diminishing the likelihood of fish being caught and injured orkilled by these gaps.

Turning now to FIG. 28, there is illustrated a turbine 18 having a hub20 and associated blades 24 which are rotatable about rotational axis26. As discussed above, to reduce injury to fish passing through turbine18, hub 20 is provided with a shroud 58 having a plurality of pockets 62formed at spaced intervals around the circumference of shroud 58. Toreduce injury to fish downstream of rotational axis 26, the downstreamregion 102 of hub 20 is configured as a sphere. As a result, when blades24 are rotated about axes 26, no gap is formed between inner edge 42 andregion 102 since inner edge 42 closely conforms to outer surface 52 ofhub 20.

Referring now to FIGS. 29-34, the present inventors have noted that itshould be possible to also improve the overall survivability of fishpassing through turbine 18--whether or not turbine 18 is alreadyprovided with features as described above designed to shield gaps formedbetween inner edge 42 and outer surface 52, and/or reduce gaps formedwith the blade outer edge or the wicket gate--by modifying theconfiguration commonly used for blades 24. Specifically, at least theregion of inner edge 42 proximate leading edge 46 (i.e., the blade edgeat portion 64) is advantageously rounded to reduce injury to the fishthat may be stricken by blade 24 (see FIG. 30) during rotation of hub20. Furthermore, inner edge 42 may also be rounded in a region 104 ofinner edge 42 extending downstream of axis 26 to trailing edge 48. Inthat case, however, and as illustrated in FIG. 31, inner edge 42 ofregion 104 need not be rounded to the same degree as inner edge 42 ofportion 64 because fish are typically carried by water flowing on waterdirecting surface 50 from leading edge 46 to trailing edge 48. Thechance of fish being stricken by inner edge 42 in region 104 istherefore much lesser than by inner edge 42 extending about portion 64.Additionally, as illustrated in FIG. 33, a portion of outer edge 44proximate leading edge 46 may also be rounded to reduce fish injury byrotation of blade 24 with hub 20. However, outer edge 44 need not berounded to the same degree along its entire length as shown in FIG. 34.This is because fish will typically be injured by the portion of outeredge 44 extending from leading edge 46.

The foregoing features, designed to increase the survivability of fishas they pass through hydroelectric turbines having adjustable blades andwicket gates, are advantageously associated with control systemsproviding traditional governor functions and control routines to ensureadequate operation of installation 10. As discussed earlier, the use ofadjustable blade turbines permits high efficiency output under a widerange of operating conditions, and in particular under various "nethead" conditions, i.e., under conditions where the difference betweenthe upper elevation source and lower elevation discharge region waterlevels varies widely. Such broad range of operating conditions typicallyrequires automatic and simultaneous adjustment of blades 24 and wicketgates 28 in accordance with load demand.

Adjusting the position of the blades and wicket gates necessitatessensing various parameters including turbine speed, wicket gateposition, blade pitch, net head, and output power, as the mostcharacteristic ones. In the early years of Kaplan turbines, sensing ofmost of these parameters was done mechanically. For example, the speedof the turbine was generally represented by the position of a flyballresponsive to the centrifugal force imparted to it by rotation of theturbine. As shown at pages 9-14 of the Woodward Governor Companytechnical specification no. 07018D covering its mechanical hydraulicgovernor, the flyball position is then compared to the position of theblade by way of a cam and associated linkage mechanism, and hydraulicsystems to provide the necessary input to the governor. Additionally,these mechanical control systems were open-loop systems, i.e., theyrequired operator interface. For example, the operator seasonally had tochange the cam used with associated linkage mechanisms to provide therepresentative net head input information.

Referring now more particularly to FIG. 35, a control system generallydesignated as 108 may advantageously be used with the variousembodiments of the present invention. Control system 108 includes aplurality of sensors 110-118 designed to measure turbine operation andother related control parameters. The electric signals generated bysensors 110-118 are sent to a controller 120, preferably via signalconditioning circuits (not shown). For example, the electrical signalrepresentative of the speed of turbine 18 is provided by a toothed discmounted on the shaft of turbine 18; the disc is associated with twoinductive sensing elements providing two independent signals tocontroller 120. Controller 120 also receives an electrical signalgenerated by sensor 112 and representative of the position of wicketgate 28. Controller 120 preferably includes a digital-based processorand required analog to digital conversion and signal scaling circuits.

The information provided by the various sensors is used in controlalgorithms allowing controller 120 to compute and generate variouscontrol signals, as required, for the efficient operation ofinstallation 10, without significantly compromising the gains in thesurvivability of fish achieved by the embodiment(s) of the presentinvention that is (are) associated with control system 108. The controlsignals generated by controller 120 are then fed to a plurality ofsignal converters generally designated as 122. The signal from eachsignal converter 122 is sent in the appropriate form to an associatedactuator which is preferably of the hydraulic-type.

As shown in FIG. 35, actuator 124 is used to adjust the position ofblades 24, while actuator 126 is used to adjust the opening of wicketgates 28, in each case as determined by controller 120, i.e., forefficient operation of turbine installation 10. However, in the attemptto further improve fish survivability as they pass through turbine 18,it may be desirable to have one signal convertor 122/actuator 126associated with each individual wicket gate 28, or alternatively with adefined group of wicket gates 28. These additional adjustmentcapabilities allow controller 120 to individually control the positionof each wicket gate 28 separately, or alternatively, to control a groupof wicket gates 28 together, using as additional parameter in thecontrol algorithms the density of fish present in the water flowingthrough turbine 18. This additional information allows controller 120 toestablish the position of blades 24 and the absolute or relativeposition of each wicket gate 28, to improve the survivability of fishpassing through turbine 18, without impairing its efficiency. In otherwords, control system 108 provides another way, whether used alone or incombination with some of the other embodiments of the present invention,to attempt to increase the survivability of fish passing through aturbine having adjustable blades and wicket gates.

It should be understood that the above description is of preferredexemplary embodiments of the present invention, and that the inventionis not limited to the specific forms described. For example, thefeatures described in the foregoing may be similarly applied to the gapformed between outer surface 52 of hub 20 and the portion of inner edge42 extending downstream of blade rotational axis 26. In addition, thoseskilled in the art will appreciate that other means may be developed todeflect fish away from gap 66, or conversely, to shield gap 66 from fishflowing through turbine 18, or to reduce the size of gap 66.Furthermore, controllers of the type associated with the described meansdo not necessarily need to be of the digital processor-based type. Suchother constructions are, nevertheless, considered to be within the scopeof this invention. Accordingly, these and any other substitutions,modifications, changes and omissions may be made in the design andarrangement of the elements and in their method of operation asdisclosed herein without departing from the scope of the appendedclaims.

We claim:
 1. A turbine with shielded gaps, the turbine comprising:a hollow hub having spaced apart inner and outer surfaces and a longitudinal axis; a plurality of runner blades, each blade comprising a hydrofoil having an inner edge and a distal outer edge, a leading edge and a trailing edge separated by a water directing surface, each blade being Pivotally connected to the hub about a rotational axis extending in a direction generally perpendicular to the longitudinal axis so that its inner edge is proximate the hub, each blade being rotatable from a maximum pitch position, in which the water directing surface is substantially parallel to the longitudinal axis, to a minimum pitch position in which the water directing surface is substantially perpendicular to the longitudinal axis; and a fabricated shroud disposed about the outer surface of the hub upstream of the rotational axes, the shroud shielding a gap formed between the hub and the inner edge of each of the blades proximate the blade leading edge as the blades approach the maximum pitch.
 2. The turbine of claim 1, wherein the turbine is disposed in a water passageway extending from an upper elevation source of water to a lower elevation discharge region, the passageway comprising a discharge ring disposed upstream of the blades, the ring having a spherical configuration cooperable with the outer edge of each of the blades as the blades are rotated about their axes to shield a gap formed between the outer edge of the blades and the passageway thereby improving the survivability of fish present in water flowing through the turbine.
 3. A turbine with shielded gaps, the turbine comprising:a hollow hub having spaced apart inner and outer surfaces and a longitudinal axis; a plurality of runner blades, each blade comprising a hydrofoil having an inner edge and a distal outer edge, a leading edge and a trailing edge separated by a water directing surface, each blade being pivotally connected to the hub about a rotational axis extending in a direction generally perpendicular to the longitudinal axis so that its inner edge is proximate the hub, each blade being rotatable from a maximum pitch position, in which the water directing surface is substantially parallel to the longitudinal axis, to a minimum pitch position in which the water directing surface is substantially perpendicular to the longitudinal axis; and means for shielding a gap formed between the hub and the inner edge of each of the blades proximate the blade leading edge as the blades are rotated from the maximum pitch to the minimum pitch; wherein the inner edge of each of the blades proximate the blade trailing edge closely conforms to and sweeps a portion of the outer surface of the hub downstream of the blade rotational axis as the blade is rotated about its rotational axis, and wherein the portion of the hub swept by the blades is configured as a sphere downstream of the blade rotational axes and configured non-spherically upstream of the blade rotational axes; and wherein the gap shielding means includes a plurality of raised areas locally formed on the outer surface in regions of the hub proximate the leading edges of the blades when the blades are at the minimum pitch.
 4. The turbine of claim 3, wherein the turbine is disposed in a water passageway extending from an upper elevation source of water to a lower elevation discharge region, the passageway comprising a discharge ring disposed upstream of the blades, the ring having a spherical configuration cooperable with the outer edge of each of the blades as the blades are rotated about their axes to shield a gap formed between the outer edge of the blades and the passageway thereby improving the survivability of fish present in water flowing through the turbine.
 5. The turbine of claim 3, wherein the inner edge of each blade is rounded in a region of the inner edge proximate at least one of the leading edge and the trailing edge.
 6. The turbine of claim 3, wherein the outer edge of each blade is rounded in a region of the outer edge proximate at least one of the leading edge and the trailing edge.
 7. A turbine with shielded gaps, the turbine comprising:a hollow hub having spaced apart inner and outer surfaces and a longitudinal axis; a plurality of runner blades, each blade comprising a hydrofoil having an inner edge and a distal outer edge, a leading edge and a trailing edge separated by a water directing surface, each blade being pivotally connected to the hub about a rotational axis extending in a direction generally perpendicular to the longitudinal axis so that its inner edge is approximate the hub, each blade being rotatable from a maximum pitch position, in which the water directing surface is substantially parallel to the longitudinal axis, to a minimum pitch position in which the water directing surface is substantially perpendicular to the longitudinal axis; and a first plurality of pockets, the pockets being formed at spaced intervals in the outer surface upstream of the rotational axes, and a second plurality of raised areas locally formed on the outer surface in regions of the hub proximate the leading edges of the blades when the blades are at the minimum pitch, wherein the pockets and the raised areas shield a gap formed between the hub and the inner edge of each of the blades proximate the blade leading edge as the blades are rotated from the maximum pitch to the minimum pitch.
 8. The turbine of claim 7, wherein the first plurality and the second plurality are equal in number.
 9. The turbine of claim 7, wherein the turbine is disposed in a water passageway extending from an upper elevation source of water to a lower elevation discharge region, the passageway comprising a discharge ring disposed upstream of the blades, the ring having a spherical configuration cooperable with the outer edge of each of the blades as the blades are rotated about their axes to shield a gap formed between the outer edge of the blades and the passageway thereby improving the survivability of fish present in water flowing through the turbine.
 10. The turbine of claim 7, wherein the inner edge of each blade is rounded in a region of the inner edge proximate at least one of the leading edge and the trailing edge.
 11. The turbine of claim 7, wherein the outer edge of each blade is rounded in a region of the outer edge proximate at least one of the leading edge and the trailing edge.
 12. A turbine with shielded gaps, the turbine comprising:a hollow hub having spaced apart inner and outer surfaces and a longitudinal axis; a plurality of runner blades, each blade comprising a hydrofoil having an inner edge and a distal outer edge, a leading edge and a trailing edge separated by a water directing surface, each blade being pivotally connected to the hub about a rotational axis extending in a direction generally perpendicular to the longitudinal axis so that its inner edge is proximate the hub, each blade being rotatable from a maximum pitch position, in which the water directing surface is substantially parallel to the longitudinal axis, to a minimum pitch position in which the water directing surface is substantially perpendicular to the longitudinal axis; means for shielding a gap formed between the hub and the inner edge of at least one of the blades proximate the blade leading edge as the blades are rotated from the maximum pitch to the minimum pitch; and a first plurality of pockets, the pockets of the first plurality being formed at spaced intervals in the outer surface downstream of the rotational axes, and a second plurality of raised areas locally formed on the outer surface in regions of the hub proximate the trailing edges of the blades when the blades are at the minimum pitch, wherein the pockets and the raised areas shield a gap formed between the hub and the inner edge of each of the blades proximate the blade trailing edge as the blades are rotated from the maximum pitch to the minimum pitch.
 13. The turbine of claim 12, wherein the first plurality and the second plurality are equal in number.
 14. The turbine of claim 12, wherein the turbine is disposed in a water passageway extending from an upper elevation source of water to a lower elevation discharge region, the passageway comprising a discharge ring disposed upstream of the blades, the ring having a spherical configuration cooperable with the outer edge of each of the blades as the blades are rotated about their axes to shield a gap formed between the outer edge of the blades and the passageway thereby improving the survivability of fish present in water flowing through the turbine.
 15. The turbine of claim 12, wherein the inner edge of each blade is rounded in a region of the inner edge proximate at least one of the leading edge and the trailing edge.
 16. The turbine of claim 12, wherein the outer edge of each blade is rounded in a region of the outer edge proximate at least one of the leading edge and the trailing edge.
 17. A hydroelectric turbine installation including a turbine with shielded gaps, the turbine installation comprising:a water passageway for containing turbine components and extending from an upper elevation source of water to a lower elevation discharge region, the passageway including a plurality of wicket gates adjustable in position to control the water flowing therethrough; a hollow hub having a longitudinal axis and spaced apart inner and outer surfaces; a corresponding plurality of blades pivotally connected to the hub, each blade being movable about a rotational axis extending in a direction generally perpendicular to the longitudinal axis, each blade comprising a hydrofoil having an inner edge disposed proximate the hub and a distal outer edge, a leading edge and a trailing edge separated by a water directing surface; wherein the hub is disposed in the passageway so that water impinges upon the leading edges and flows along the water directing surfaces past the trailing edges as water passes through the passageway from the upper elevation source; an electrical closed-loop control system for adjusting each blade in position from a maximum pitch position, in which the water directing surface is substantially parallel to the longitudinal axis, to a minimum pitch position in which the water directing surface is substantially perpendicular to the longitudinal axis; and means for shielding a gap formed between the hub and the inner edge of each of the blades as the blades are rotated from the maximum pitch to the minimum pitch; wherein the control system includes a digital-based processor controller associated with sensors selectively generating electrical signals indicative of at least turbine speed, blade pitch, and difference in elevation between the upper elevation source of water and the lower elevation discharge region.
 18. The turbine of claim 17, wherein the gap shielding means includes a plurality of raised areas locally formed on the outer surface in regions of the hub proximate the trailing edges of the blades when the blades are at the minimum pitch.
 19. The turbine of claim 17, wherein the inner edge of each of the blades proximate the blade trailing edge closely conforms to and sweeps a portion of the outer surface of the hub as the blade is rotated about its rotational axis, and wherein the portion of the hub swept by the blades is configured as a sphere downstream of the rotational axes.
 20. The turbine of claim 17, wherein the gap shielding means includes a plurality of raised areas locally formed on the outer surface in regions of the hub proximate the leading edges of the blades when the blades are at the minimum pitch.
 21. The hydroelectric turbine installation of claim 17, the sensors further selectively generating electrical signals indicative of wicket gate position, and the controller capable of generating signals for adjusting in position the blades and wicket gates.
 22. The hydroelectric turbine installation of claim 21, the sensors further selectively generating an electrical signal indicative of a density of fish present in the water.
 23. The hydroelectric turbine installation of claim 17, the sensors further selectively generating electrical signals indicative of a density of fish present in the water.
 24. The turbine of claim 17, wherein the passageway comprises a discharge ring disposed upstream of the blades, the ring having a spherical configuration cooperable with the outer edge of each of the blades as the blades are rotated about their axes to shield a gap formed between the outer edge of the blades and the passageway thereby improving the survivability of fish present in water flowing rough the turbine.
 25. The turbine of claim 17, wherein the inner edge of each blade is rounded in a region of the inner edge proximate at least one of the leading edge and the trailing edge.
 26. The turbine of claim 17, wherein the outer edge of each blade is rounded in a region of the outer edge proximate at least one of the leading edge and the trailing edge.
 27. A hydroelectric turbine installation including a turbine with shielded gaps, the turbine installation comprising:a water passageway for containing turbine components and extending from an upper elevation source of water to a lower elevation discharge region, the passageway including a plurality of wicket gates adjustable in position to control the water flowing therethrough; a hollow hub having a longitudinal axis and spaced apart inner and outer surfaces; a corresponding plurality of blades pivotally connected to the hub, each blade being movable about a rotational axis extending in a direction generally perpendicular to the longitudinal axis, each blade comprising a hydrofoil having an inner edge disposed proximate the hub and a distal outer edge, a leading edge and a trailing edge separated by a water directing surface; wherein the hub is disposed in the passageway so that water impinges upon the leading edges and flows along the water directing surfaces past the trailing edges as water passes through the passageway from the upper elevation source; an electrical closed-loop control system for adjusting each blade in position from a maximum pitch position, in which the water directing surface is substantially parallel to the longitudinal axis, to a minimum pitch position in which the water directing surface is substantially perpendicular to the longitudinal axis; and means for shielding a gap formed between the hub and the inner edge of each of the blades as the blades are rotated from the maximum pitch to the minimum pitch; wherein the hub further comprises a plurality of pockets formed at spaced intervals in the outer surface upstream of the rotational axes, a portion of the leading edge of each of the blades being progressively received in a respective pocket as the blades are rotated by the control system from the minimum pitch to the maximum pitch.
 28. The turbine of claim 27, wherein the passageway comprises a discharge ring disposed upstream of the blades, the ring having a spherical configuration cooperable with the outer edge of each of the blades as the blades are rotated about their axes to shield a gap formed between the outer edge of the blades and the passageway thereby improving the survivability of fish present in water flowing through the turbine.
 29. A hydroelectric turbine installation including a turbine with shielded gaps, the turbine installation comprising:a water passageway for containing turbine components and extending from an upper elevation source of water to a lower elevation discharge region, the passageway including a plurality of wicket gates adjustable in position to control the water flowing therethrough; a hollow hub having a longitudinal axis and spaced apart inner and outer surfaces; a corresponding plurality of blades pivotally connected to the hub, each blade being movable about a rotational axis extending in a direction generally perpendicular to the longitudinal axis, each blade comprising a hydrofoil having an inner edge disposed proximate the hub and a distal outer edge, a leading edge and a trailing edge separated by a water directing surface; wherein the hub is disposed in the passageway so that water impinges upon the leading edges and flows along the water directing surfaces past the trailing edges as water passes through the passageway from the upper elevation source; an electrical closed-loop control system for adjusting each blade in position from a maximum pitch position, in which the water directing surface is substantially parallel to the longitudinal axis, to a minimum pitch position in which the water directing surface is substantially perpendicular to the longitudinal axis; and means for shielding a gap formed between the hub and the inner edge of each of the blades as the blades are rotated from the maximum pitch to the minimum pitch; wherein the hub further comprises a plurality of pockets formed at spaced intervals in the outer surface downstream of the rotational axes and wherein a portion of the trailing edge of each of the blades is progressively received in a respective downstream pocket as the blades are rotated by the control system from the minimum pitch to the maximum pitch.
 30. The turbine of claim 29, wherein the passageway comprises a discharge ring disposed upstream of the blades, the ring having a spherical configuration cooperable with the outer edge of each of the blades as the blades are rotated about their axes to shield a gap formed between the outer edge of the blades and the passageway thereby improving the survivability of fish present in water flowing through the turbine.
 31. A method for improving the survivability of fish present in water flowing from an upper elevation source to a lower elevation discharge region through a water passageway of a turbine of the type comprising a hollow hub having a longitudinal axis and spaced apart inner and outer surfaces, a corresponding plurality of blades pivotally connected to the hub, each blade being movable about a rotational axis extending in a direction generally perpendicular to the longitudinal axis, each blade comprising a hydrofoil having an outer edge and a distal inner edge disposed proximate the hub, a leading edge and a trailing edge separated by a water directing surface, the method comprising the steps of:positioning the hub in the passageway so that water impinges upon the leading edges and flows along the water directing surfaces past the trailing edges as water passes through the passageway from the source to the discharge region; and providing means for shielding a gap formed between the inner edge of each of the blades proximate the blade leading edge and the outer surface of the hub as the blades rotate from maximum to minimum pitch; wherein the step of providing the gap shielding means includes at least one of the following steps:fabricating a shroud about the outer surface of the hub upstream of the rotational axes, the shroud shielding the inner edge of each of the blades proximate the blade leading edge as the blades approach the maximum pitch; and forming a plurality of pockets at spaced intervals in the outer surface upstream of the rotational axes, a portion of the leading edge of each of the blades being progressively received in a respective pocket as the blades are rotated from the minimum pitch to the maximum pitch.
 32. The method of claim 31, further including the step of providing means for reducing discharge gaps formed between wicket gates disposed in the passageway to control water flow and a discharge ring disposed upstream of the blade rotational axes.
 33. The method of claim 31, further including the step of providing means for shielding a gap formed between the outer edge of each of the blades and the passageway.
 34. A turbine with shielded gaps, comprising:a hollow hub having spaced apart inner and outer surfaces and a longitudinal axis; a plurality of runner blades, each blade comprising a hydrofoil having an inner edge and a distal outer edge, a leading edge and a trailing edge separated by a water directing surface, each blade being pivotally connected to the hub about a rotational axis extending in a direction generally perpendicular to the longitudinal axis so that its inner edge is proximate the hub, each blade being rotatable from a maximum pitch position, in which the water directing surface is substantially parallel to the longitudinal axis, to a minimum pitch position in which the water directing surface is substantially perpendicular to the longitudinal axis; and a fabricated shroud disposed about the outer surface of the hub upstream of the rotational axes, the shroud shielding a gap formed between the hub and the inner edge of each of the blades proximate the blade leading edge as the blades approach the maximum pitch; wherein the inner edge of each of the blades proximate the blade trailing edge closely conforms to and sweeps a portion of the outer surface of the hub downstream of the blade rotational axis as the blade is rotated about its rotational axis, and wherein the portion of the hub swept by the blades is configured as a sphere downstream of the blade rotational axes.
 35. The turbine of claim 34, wherein the turbine is disposed in a water passageway extending from an upper elevation source of water to a lower elevation discharge region, the passageway comprising a discharge ring disposed upstream of the blades, the ring having a spherical configuration cooperable with the outer edge of each of the blades as the blades are rotated about their axes to shield a gap formed between the outer edge of the blades and the passageway thereby improving the survivability of fish present in water flowing through the turbine.
 36. A turbine with shielded gaps, comprising:a hollow hub having spaced apart inner and outer surfaces and a longitudinal axis; a plurality of runner blades, each blade comprising a hydrofoil having an inner edge and a distal outer edge, a leading edge and a trailing edge separated by a water directing surface, each blade being pivotally connected to the hub about a rotational axis extending in a direction generally perpendicular to the longitudinal axis so that its inner edge is proximate the hub, each blade being rotatable from a maximum pitch position, in which the water directing surface is substantially parallel to the longitudinal axis, to a minimum pitch position in which the water directing surface is substantially perpendicular to the longitudinal axis; and a plurality of pockets formed at spaced intervals in the outer surface upstream of the rotational axes, a portion of the leading edge of each of the blades being progressively received in a respective pocket as the blades are rotated from the minimum pitch to the maximum pitch to thereby shield a gap formed between the hub and the inner edge of each of the blades; wherein the inner edge of each of the blades proximate the blade trailing edge closely conforms to and sweeps a portion of the outer surface of the hub downstream of the blade rotational axis as the blade is rotated about its rotational axis, and wherein the portion of the hub swept by the blades is configured as a sphere downstream of the blade rotational axes. 